1. Field of the Invention
The invention relates to a golf club grip and a manufacturing method thereof, more particularly to a single sheet natural leather golf club grip with an axial seam structure and a manufacturing method thereof.
2. Description of the Related Art
The Applicant Hong-Sung Chu has successfully developed a single sheet anti-slip skin golf club grip with closed-cell foam tubular inner body with light weight, adequate rigidity and resilience, sufficient shock absorbing properties, and ease of installation (U.S. Pat. No. 6,656,057 filed on Jan. 23, 2002, granted to Manuel & The Applicant Hong-Sung Chu on Dec. 2, 2003). The Applicant Hong-Sung Chu has further developed a hem structure for a single sheet anti-slip skin layered golf club grip for finishing and hemming the marginal edges of a winding sheet layer (U.S. Pat. No. 6,908,400 filed on Aug. 5, 2003, granted to The Applicant Hong-Sung Chu & Chia-Hung Wu on Jun. 21, 2005, Now Expired). Two above mentioned U.S. patent's single sheet anti-slip skin that can be natural leather, synthetic leather, or Polyurethane synthetic leather.
Referring to FIG. 1, a golf club grip 1 is disclosed in a sixth embodiment of U.S. Pat. No. 6,908,400 FIG. 17, 18, 19 (not shown). The grip 1 has a seam straightening rib 111 located between its cap and protective rim so that two axial margins 101, 102 meet each other along a straight line defined by the seam straightening rib 111. An axial seam 13 is thus defined by the axial margins 101, 102. A seam strip 12 is inset bonded within a receiving groove 14 to finish the axial seam 13. This grip 1 has the flaws that are as followed:
1.) When the sheet layer 10 is wrapped around an inner sleeve body 11, there is a possibility that two axial margins 101,102 will form either a ridged 103 (FIG. 2) or an overlapped surface 104 (FIG. 3). This is due to the elasticity of the Polyurethane synthetic leather sheet layer 10. This ridged surface 103 or overlapped surface 104 will cause the seam strip 12 inset bonded improperly within the receiving groove 14 thereby increasing the manufacture defective rate during production.
2.) Its grip material of the sheet layer 10 is limited to the Polyurethane synthetic leather which is inferior to natural leather as a golf club grip material. (detailed as followed).
Golf club grips are the only direct link between the golf club and the player's body. The golf swing has been described as a “violent movement”. Players must exert enough force on the golf club to enable the club head to travel fast and to make square contact with the ball at impact. It is thus imperative that the grip is made for the purpose of assisting a player to obtain a firm hold with torque resistance. In order to prevent the club from slipping or twisting out of the player's hands, it is crucial for the grip material, in its attempt to be an anti-slip skin layer, to have a soft and firm touch for slip resistance, stiff or dense gradient in structure for torque resistance, and a durable gripping surface.
The sixth embodiment of U.S. Pat. No. 6,908,400's Polyurethane synthetic leather is one of the conventional synthetic resin (polymers) leathers. Synthetic resin (polymers) leather and natural leather are very different structure wise. FIG. 4 shows a synthetic resin (polymers) leather 50 including an outer resin (polymers) layer 501, an inner base layer 502, and a binding layer 503. Polyurethane 501P can be an example of an outer resin (polymers) layer 501. The inner base layer 502 is made of man-made fibres 506 such as felt 502F, non-woven/woven fiber, textile, fabric or other artificial fibrous materials compounding with resin (polymers). The binding layer 503 is between the outer resin (polymers) layer 501 and the inner base layer 502. FIG. 6 is a Scanning Electronic Microscopic (SEM) 60× magnified picture of a Polyurethane/Felt synthetic resin leather which has a polyurethane layer 501P as its outer resin (polymers) layer 501, a felt layer 502F as its inner base layer 502, and its binding layer 503. Natural leather 52 is a material made from the hide or skin of animals by tanning processes. This skin is preferably cowhide, calf skin, sheep skin, or pig skin. The tanning process makes the potentially biodegradable skin into a long lasting and versatile natural material for various uses. Referring to FIGS. 5 and 7, natural leather 52 is composed of natural collagen fiber bundles 524 and has a fiber thickness and degree of interweaving which changes continuously. The collagen fiber bundles 524 stereoscopic structure consists of single collagen fibres 525 that twist with each other in a dense gradient manner. Natural leather 52 includes a grain layer 521 as a surface layer and an inner reticular layer 522 as a base layer. The grain layer 521 is thin yet dense in structure, covered with drawn tight collagen fiber surface 523 and has a natural brook web-like pattern. The inner reticular layer 522 is composed of the collagen fiber bundles 524, and has almost no boundary between the grain layer 521 and itself.
Referring to FIGS. 4 to 7, three differences in structure and features between synthetic resin (polymers) leather 50 and natural leather 52 are as followed:
1.) Surface Layer: Synthetic resin (polymers) leather 50's outer resin (polymers such as Polyurethane) layer 501 is used to simulate the grain layer 521 of natural leather 52. Its thickness is far thicker than the natural leather grain layer 521 and surface patterns are regular and uniform, lacking of the natural leather grain layer 521's brook web-like patterns. Therefore, outer resin (polymers such as Polyurethane) layer 501 has a soft, spongy feel with a cool plastic smooth touch, while, natural leather grain layer 521 features unique soft, firm look and feel.
2.) Base Layer: Synthetic resin (polymers) leather 50's inner base layer 502 is made out of man-made fibres 506 such as felt, nylon, textile, fabric or compound of polymers (such as Polyurethane) and other such artificial fibres to simulate natural leather 52's inner reticular layer 522. Due to the uniform orientation and interweaving structure of synthetic resin (polymers) leather inner base layer 502, the fibres of synthetic resin (polymers) leather is relatively loose. Conversely, natural leather inner reticular layer 522 is a dense interwoven material with the collagen fiber bundles 524 as mentioned above. Because of this, in regards to torque resistance for the golf club grip, synthetic resin (polymers) leather inner base layer 502 is much weaker than natural leather inner reticular layer 522.
3.) Transitive Layer: Synthetic resin (polymers) leather 50 has a weak binding layer 503 between the outer resin (polymers such as Polyurethane) layer 501's inner surface 504 and the inner base layer 502's outer surface 505. Outer resin (polymers such as Polyurethane) layer 501 tends to peel off from inner base layer 502 due to the weak binding layer 503. Natural leather 52 has no obvious boundary between the surface grain layer 521 and the inner reticular layer 522.
Above are the three most crucial differences in structure concerning the grip material in regards to the features in mind (soft, firm look and feel, dense in structure for torque resistance, and a durable gripping surface). None of the conventional synthetic resin (polymers) leathers 50 can compete with natural leather 52. Since natural leather 52 is denser and stiffer than synthetic resin (polymers) leather 50 material wise, the two axial margins of the natural leather sheet are harder to hold together than the synthetic resin (polymers) leather sheet in an axial seam of a single sheeted golf club grip. Therefore, it is the present invention's object to provide an improved axial seam structure to firmly hold a single sheet natural leather for use as a golf club grip (to be detailed later).
Aside from the grip 1 (FIG. 1), there are three other types of an axial seam structure for single sheet leather golf club grips. They are as follows:
1.) Sewn Axial Seam: Referring to FIG. 8, a single sheet golf club grip 2 is disclosed in U.S. Pat. No. 3,366,384 FIGS. 6 and 11 (not shown). The grip 2 has its single sheet leather 21's two axial edges 212, 213 inwardly sewn together by threads 22 face to face to form an axial seam 24.
2.) Adhered Axial Seam: FIG. 9, 10 both show a single sheet golf club grip 3, which is disclosed in U.S. Pat. No. 3,857,745 FIG. 5 (not shown). The grip 3 has its single sheet leather 31's two skived axial edges 312,313 adhered together through a skived overlapped adhesive joint 34 at a skived angle from the outer surface of one axial edge 313 to the inner surface of the opposing end of the axial edge 312 to form an axial seam 33. The two axial edges 312, 313 are also brought together face to face. Due to the skived and limited adherence surface of the two skived axial edges 312, 313, the bonding strength of axial seam 33 is very weak. This flaw is even more obvious if the single sheet natural leather 52 is used as a golf club grip material. This is due to the fact that the skived surface of said sheet of natural leather is made of natural collagen fiber bundles which are a non polymeric material with skived and limited adherence surface. It is the fact that non polymeric material is harder to adhere together than polymeric-layered synthetic resin (polymers) leathers. These two skived axial edges 312, 313 tend to burst out along the axial seam 33 during the installation of the grip 3. Also, along the skived axial edge 313, a sharp skived border 314 will be exposed on the surface of the grip 3. This sharp skived border 314 is so frail that the player's gripping fingers can easily tear it. Therefore, this Adhered Axial seam 33 needs a reinforcement mentioned in the next description.
3.) Reinforce-Adhered Axial Seam: Referring to FIG. 11, a single sheet golf club grip 4 has its two skived axial edges 412, 413 adhered together face to face through a skived overlapped adhesive joint 46. Both edges are then heat pressed to form a depressed reinforcement channel 45 which may be deposited with hot polyurethane 43 to form an axial seam 44. The grip 4 is disclosed in U.S. Pat. No. 7,491,133 FIGS. 45 and 65 (not shown).
The above prior arts, the grips 2, 3, 4, have two elements in common. Their axial edges 212/213, 312/313, 412/413 are brought together by either sewing or adhering them face to face and their inner surfaces' 211, 311, 411 configurations of the sheet layers 21,31, 41 relatively correspond to the outer surfaces' 231, 321, 421 shapes and dimensions of their sleeve body 23, 32, 42. These two elements will result in limiting their sleeve bodies' 23, 32, 42 expansion capacity during the installation of the grips 2, 3, 4, making it difficult to install the grips 2, 3, 4 onto the golf club shafts. This limited expansion also means that it is hard to increase the maximum grip size attainable which is an adjustment usually done by applying additional build up tape.
In regards to The Applicant Hong-Sung Chu previous invention U.S. Pat. No. 6,908,400 sixth embodiment's PU or PVC seam strip 13 in FIG. 1 and the prior art U.S. Pat. No. 7,491,133's axial channel 45 deposited with hot polyurethane 43 in FIG. 4, there is one particular flaw in appearance—they are obviously imitations of natural leather 52. This detracts from the natural beauty of the single sheet natural leather golf club grip.